Flame-retardant polycarbonate resin composition and electrical and electronic components made by molding the same

ABSTRACT

A flame-retardant polycarbonate resin composition, characterized by comprising a polycarbonate resin (A) and a composite rubbery graft copolymer (B), preferably one obtained by grafting a composite rubber having a structure constituted of 1 to 99 wt. % of a polyorganosiloxane rubber component and 99 to 1 wt. % of a polyalkyl acrylate rubber component, the two components being so interwisted with each other as not to separate from each other, and a mean particle diameter of 0.01 to 0.6 μm with one or more vinyl monomers, at an (A) to (B) weight ratio of 99:1 to 90:10, and by containing, per 100 parts by weight of the sum total of the components (A) and (B), 0.3 to 1.2 parts by weight (in terms of phosphorus) of a halogen-free phosphoric ester (C) and 0.01 to 1.0 part by weight of polytetrafluoroethylene (D), the weight ratio of the graft copolymer (B) to the phosphorus resulting from the phosphoric ester (C) lying within the range of 2 to 15; and housing of office automation equipment and electrical and electronic appliances and battery packs made by molding the composition. The composition is improved in mechanical properties such as impact resistance, is excellent in moldability and flowability, and exhibits high flame retardance even without resort to any bromine compound.

TECHNICAL FIELD

The present invention relates to a flame-retardant polycarbonate resincomposition and to electrical and electronic components of housings ofoffice automation equipment, housings of electrical and electronicappliances and battery packs as made by molding the composition. Moreprecisely, it relates to a flame-retardant, non-bromine polycarbonateresin composition having good flame retardancy, good mechanicalproperties including impact resistance, good flowability and goodmoldability, and to housings of office automation equipment, housings ofelectrical and electronic appliances and battery packs as made bymolding the composition.

BACKGROUND OF THE INVENTION

As having good mechanical properties (especially high impactresistance), good electric properties, and good transparency,polycarbonate resins are widely used as engineering plastics in variousfields of office automation equipment, electrical and electronicappliances, building materials, etc.

Among various thermoplastic resins, polycarbonate resins have a highoxygen index and are generally self-extinguishable. However, especiallyin the fields of office automation equipment and electrical andelectronic appliances, concretely for applications to housings of officeautomation equipment, to housings of electrical and electronicinstruments such as notebook-type personal computers and others, and tobattery packs, resin compositions with much more improved flameretardancy are desired to satisfy the requirement for safety operationof those equipment and appliances.

For making resins have flame retardancy, heretofore, flame retardantscomprising a bromine compound have been used. One problem with resincompositions that comprise such a bromine-containing flame retardant isthat molds used for repeatedly molding the resin compositions are rustedand that the resin compositions being molded are yellowed while inmolds. Another problem is that the resin compositions being moldedrelease corrosive gases that may pollute the environment. In thatsituation, non-bromine flame retardants are being much desired for resincompositions.

On the other hand, office automation equipment and electrical andelectronic appliances, concretely, their housings and battery packs arerequired to have much improved impact resistance. In order to improvethe impact resistance of such equipment and appliances, concretely theircomponents, one popular means that has heretofore been generallyemployed is to add rubbery improvers to polycarbonate resins and to moldthe resulting resin compositions. However, this is problematic in thatthe resin compositions to which is added a large amount of such animpact resistance improver could not have good flame retardancy. Fortheir applications, in particular, battery packs are used for mobilecommunication appliances such as portable telephones and others or forportable terminals such as notebook-type personal computers and others,and are therefore required to be lightweight and thin-walled.Accordingly, the materials for such battery packs are required to havegood moldability and flowability.

Various techniques for those requirements have heretofore been proposed,for example, in JP-A 07-173401, 08-259792, 08-120169, 07-304943,08-239565, etc. The compositions proposed therein could have flameretardancy in some degree, but are still problematic in that theycontain bromine-containing flame retardants, or if not containingbromine-containing flame retardants, their mechanical properties such asimpact resistance and also their moldability and flowability are poor.

The object of the invention is to provide a polycarbonate resincomposition having improved mechanical properties such as impactresistance, having good moldability and flowability and having goodflame retardancy even though not containing a bromine compound, and toprovide housings of office automation equipment, housings of electricaland electronic appliances and also battery packs as made by molding thecomposition.

DISCLOSURE OF THE INVENTION

Given that situation, we, the present inventors have assiduouslystudied, and, as a result, have found that the object can be attained byadding a composite rubbery graft copolymer to a polycarbonate resin,preferably by adding a specific composite rubbery graft copolymer, ahalogen-free phosphoric ester and a polytetrafluoroethylene thereto in aspecific ratio of the composite rubbery graft copolymer to thehalogen-free phosphoric ester.

The invention has been completed on the basis of these findings.

Specifically, the invention provides a polycarbonate resin composition,and housings of office automation equipment, housings of electrical andelectronic appliances, and battery packs as made by molding thecomposition, which are as follows:

(1) A flame-retardant polycarbonate resin composition comprising (A) apolycarbonate resin and (B) a composite rubbery graft copolymer in aratio by weight, (A):(B), falling between 99:1 and 90:10, andcontaining, relative to 100 parts by weight of the sum total of thecomponent (A) and the component (B), (C) from 0.3 to 1.2 Darts byweight. in terms of phosphorus. of a halogen-free phosphoric ester, and(D) from 0.01 to 1.0 part by weight of a polytetrafluoroethylene, inwhich the ratio by weight of the amount of the composite rubbery graftcopolymer (B) to the phosphorus content of the halogen-free phosphoricester (C) falls between 2 and 15.

(2) The flame-retardant polycarbonate resin composition of (1), whereinthe composite rubbery graft copolymer (B) is prepared by grafting acomposite rubber, which has a structure composed of from 1 to 99% byweight of a polyorganosiloxane rubber component and from 1 to 99% byweight of a polyalkyl acrylate rubber components, the two componentsbeing so intertwisted with each other as not to separate from eachother, and has a mean particle diameter of from 0.01 μm to 0.6 μm, withone or more vinyl monomers.

(3) Electrical and electronic components as made by molding theflame-retardant polycarbonate resin composition of (1) or (2).

(4) Housings of office automation equipment, or housings of electricaland electronic appliances, as made by molding the flame-retardantpolycarbonate resin composition of (1) or (2).

(5) Battery packs as made by molding the flame-retardant polycarbonateresin composition of (1) or (2).

BEST MODES OF CARRYING OUT THE INVENTION

The invention is described in detail hereinunder.

1. Flame-Retardant Polycarbonate Resin Composition

(1) Description of Constituent Components

[i] Polycarbonate Resin (Component (A))

In the flame-retardant polycarbonate resin composition of the invention,the polycarbonate resin for the component (A) may be any and every onethat may be prepared in any ordinary method of, for example, reacting adiphenol with a polycarbonate precursor such as phosgene, carbonatecompounds, etc. Concretely, it includes polycarbonate resins as preparedthrough reaction of a diphenol with a carbonate precursor such asphosgene or transesterification of a diphenol with a carbonate precursorsuch as diphenyl carbonate, in a solvent of methylene chloride or thelike in the presence of a known acid acceptor and a known molecularweight-controlling agent, to which is optionally added a branchingagent.

For the reaction, various diphenols are employable. Especially preferredis 2,2-bis (4-hydroxyphenyl)propane (this is generally referred to asbisphenol A). As other bisphenols employable herein in addition tobisphenol A, mentioned are bis (hydroxyaryl) alkanes such as bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane,2,2-bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-1-methylphenyl)propane,bis(4-hydroxyphenyl)naphthylmethane,1,1-bis(4-hydroxy-t-butylphenyl)propane,2,2-bis(4-hydroxy-3,5-tetramethylphenyl)propane, etc.;bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane, etc.; dihydroxyarylethers such as 4,4′-dihydroxyphenyl ether,4,4′-dihydroxy-3,3′-dimethylphenyl ether, etc.; dihydroxydiaryl sulfidessuch as 4,4′-dihydroxydiphenyl sulfide,4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide, etc.; dihydroxydiarylsulfoxides such as 4,4′-dihydroxydiphenyl sulfoxide,4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide, etc.; dihydroxydiarylsulfones such as 4,4′-dihydroxydiphenyl sulfone,4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfone, etc.; dihydroxydiphenylssuch as 4,4′-dihydroxydiphenyl, etc. One or more of these diphenols maybe used either singly or as combined.

The carbonate compound includes, for example, diaryl carbonates such asdiphenyl carbonate, etc.; dialkyl carbonates such as dimethyl carbonate,diethyl carbonate, etc.

As the molecular weight-controlling agent, herein employable is any andevery one that may be used in polymerization to give polycarbonates.Concretely mentioned are monophenols which include, for example, phenol,o-n-butylphenol, m-n-butylphenol, p-n-butylphenol, o-isobutylphenol,m-isobutylphenol, p-isobutylphenol, o-t-butylphenol, m-t-butylphenol,p-t-butylphenol, o-n-pentylphenol, m-n-pentylphenol, p-n-pentylphenol,o-n-hexylphenol, m-n-hexylphenol, p-n-hexylphenol, p-t-octylphenol,o-cyclohexylphenol, m-cyclohexylphenol, p-cyclohexylphenol,o-phenylphenol, m-phenylphenol, p-phenylphenol, o-n-nonylphenol,m-nonylphenol, p-n-nonylphenol, o-cumylphenol, m-cumylphenol,p-cumylphenol, o-naphthylphenol, m-naphthylphenol, p-naphthylphenol,2,5-di-t-butylphenol, 2,4-di-t-butylphenol, 3,5-di-t-butylphenol,2,5-dicumylphenol, 3,5-dicumylphenol, p-cresol, etc. Of thosemonophenols, preferred are p-t-butylphenol, p-cumylphenol,p-phenylphenol, etc.

As the branching agent, for example, employable are compounds having atleast three functional groups, such as1,1,1-tris(4-hydroxyphenyl)ethane, α, α′,α″-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene,1-[α-methyl-α-(4′-hydroxyphenyl)ethyl]-4-[α′,α′-bis(4″-hydroxyphenyl)ethyl]benzene, phloroglucinol, trimellitic acid,isatinbis(o-cresol), etc.

In general, the polycarbonates for use in the invention preferably havea viscosity-average molecular weight of from 10,000 to 100,000, morepreferably from 14,000 to 40,000.

[ii] Composite Rubbery Graft Copolymer (Component (B))

The composite rubbery graft copolymer of the component (B) is one asprepared by grafting a composite rubber with one or more vinyl monomers.Preferably, it is prepared by grafting a composite rubber, which has astructure composed of from 1 to 99% by weight of a polyorganosiloxanerubber component and from 1 to 99% by weight of a polyalkyl acrylaterubber components, the two components being so intertwisted with eachother as not to separate from each other, and has a mean particlediameter of from 0.01 μm to 0.6 μm, with one or more vinyl monomers.

The composite rubbery graft copolymer may be produced in any knownmanner, for example, according to the methods described in JP-A64-79257and 1-190746. For producing it, for example, a polyorganosiloxane rubberlatex is first prepared, and monomers for polyalkyl (meth)acrylaterubbers are infiltrated into rubber particles in the polyorganosiloxanerubber latex, and then polymerized in the rubber particles.

The polyorganosiloxane rubber may be prepared by mixing a linearorganosiloxane such as dimethylsiloxane or the like with from 0.1 to 30%by weight of a polyfunctional, silane-based crosslinking agent such astrimethoxymethylsilane, tetraethoxysilane or the like, and polymerizingthem in emulsion.

For the latex production, usable is the method disclosed in U.S. Pat.No. 2,891,920. According to the method, the emulsion polymerization maybe effected by mixing the components noted above in water, in thepresence of a sulfonic acid-based emulsifier such as analkylbenzenesulfonic acid, an alkylsulfonic acid or the like, which actsalso as a polymerization initiator, for example, in a homogenizer.

The resulting polyorganosiloxane rubber latex is then neutralized withan aqueous alkali solution of sodium hydroxide or the like, to which areadded an alkyl (meth)acrylate such as methyl acrylate, n-butylacrylateor the like, a crosslinking agent such as ethylene glycol dimethacrylateor the like, and a grafting reaction promoter such as allyl methacrylateor the like. In that condition, those additives are infiltrated into thepolyorganosiloxane rubber particles. Next, an ordinary radicalpolymerization initiator is added thereto, and the monomers arepolymerized to give a composite rubber latex in which the crosslinkedpolyalkyl (meth)acrylate rubber structure formed is intertwisted withthe crosslinked polyorganosiloxane rubber structure so that the tworubber components are substantially unseparable.

To the composite rubber latex, added are vinyl monomers (e.g., alkenylaromatic compounds such as styrene, etc.; methacrylates such as methylmethacrylate, etc.; acrylates such as methyl acrylate, etc.; vinylcyanides such as acrylonitrile, etc.), and these are radical-polymerizedin a single-stage or multi-stage polymerization manner. Then, calciumchloride or the like is added to the resulting latex for salting out toobtain the intended, composite rubbery graft copolymer throughsolidification and isolation.

[iii] Halogen-Free Phosphoric Ester (Component (C))

The halogen-free phosphoric ester of the component (C) for use in theinvention does not contain a halogen atom such as bromine or the like.Therefore, the scrap of the moldings of the composition of the inventionpollutes little the environment.

The halogen-free phosphoric ester includes, for example, monophosphatesor polyphosphates of the following general formula (I):

In formula (I), R¹ to R⁴ each independently represent anoptionally-substituted aryl group, and these may be the same ordifferent; X represents an optionally-substituted arylene group; a, b, cand d each represent 0 or 1; and p represents an integer of from 0 to 5.Where two or more phosphates are used, as combined, p in formula (I)shall be the average of p in plural phosphates. The substituents for thearyl and arylene groups include, for example, an alkyl group having from1 to 10 carbon atoms, an alkoxy group having from 1 to 10 carbon atoms,an aryl group such as phenyl, tolyl, etc. The aryl and arylene groupsmay have one or more substituents.

Specific examples of the halogen-free phosphates of formula (I) includemonophosphates such as triphenyl phosphate, tricresyl phosphate,trixylenyl phosphate, tribiphenyl phosphate, etc.; and polyphosphatessuch as phenyl-resorcinol polyphosphate, phenyl-hydroquinonepolyphosphate, phenyl-cresyl-resorcinol polyphosphate,phenyl-cresyl-hydroquinone polyphosphate, tetraphenyl-resorcinoldiphosphate, tetraphenyl-hydroquinone diphosphate,phenyl-tricresyl-resorcinol diphosphate, phenyl-tricresyl-hydroquinonediphosphate, tetrabiphenyl-resorcinol diphosphate,tetrabiphenyl-hydroquinone diphosphate, etc. Of those, preferred arepolyphosphates, as being effective for preventing the polycarbonateresin composition comprising them from adhering to molds and fromsoiling molds while the composition is thermally molded. One or more ofthese monophosphates and polyphosphates may be used either singly or ascombined.

[iv] Polytetrafluoroethylene (Component (D))

Polytetrafluoroethylene (PTFE) of the component (D) is to prevent thepolycarbonate resin composition comprising it from melting and drippingand to make the composition have good flame retardancy. Therefore, PTFEwith good fibrillating ability is preferably used.

The fibrillating ability of PTFE is meant to indicate that PTFE couldfibrillate after having received shear stress of plasticization whilethe composition comprising it is kneaded or molded through injection,and this brings about high flame retardancy of the moldings of thecomposition.

PTFE with such fibrillating ability for use in the invention is notspecifically defined. For example, preferred are those that are groupedin Type 3 in the ASTM standard. As specific examples ofcommercially-available products of PTFE grouped in Type 3, mentioned areTeflon 6-J (trade name, from Mitsui-DuPont Fluorochemical), Polyflon TFED-1 (trade name, from Daikin Industry), Polyflon TFE F-104 (trade name,from Daikin Industry), etc. As others not in Type 3 but are employableherein, for example, mentioned are Algoflon F5 (trade name,fromMontefluos), PolyflonMPA FA-110 and Polyflon TFE F201 (both tradenames, from Daikin Industry), etc.

Two or more of those PTFEs maybe used, as combined. PTFEs withfibrillating ability such as those mentioned above may be prepared, forexample, by polymerizing tetrafluoroethylene in an aqueous medium in thepresence of sodium, potassium or ammonium peroxydisulfide, under apressure falling between 1 and 100 psi and at a temperature fallingbetween 0 and 200° C., preferably between 20 and 100° C.

(2) Proportions of Constituent Components

[i] Regarding the proportions of the polycarbonate resin (A) and thecomposite rubbery graft copolymer (B), the ratio by weight of (A) to (B)falls between 99:1and 90:10, but preferably between 99:1 and 92:8. Withthe proportion of the composite rubbery graft copolymer being at least 1in terms of the ratio noted above, the moldings of the composition couldhave satisfactory impact resistance. However, if the proportion of thecomposite rubbery graft copolymer is larger than 10 in terms of thatratio, a large amount of the flame retardant must be added to thecomposition in order not to lower the flame retardancy of thecomposition. If so, the impact resistance of the moldings of thecomposition will lower. With the proportion of the polycarbonate resinbeing at least 90 in terms of the ratio noted above, the compositionwell exhibits the properties of polycarbonates.

[ii] Regarding the proportion of the halogen-free phosphoric ester ofthe component (C), the amount of the component (C) is from 0.3 to 1.2parts by weight relative to 100 parts by weight of the sum total of thecomponent (A) and the component (B). The component (C) exhibits asynergistic effect for improving the flowability of the composition, andis effective for preventing the moldings of the composition from havingsilver marks. If the amount of the component (C) is smaller than 0.3parts by weight, the composition could not have satisfactory flameretardancy; and if larger than 1.2 parts by weight, the composition willlose the characteristics of polycarbonates, in particular, the impactresistance of the moldings of the composition will be poor. Therefore,adding the component (C) to the composition in an amount oversteppingthe defined range is unfavorable.

[iii] Regarding the proportion of the polytetrafluoroethylene of thecomponent (D), the amount of the component (D) is from 0.01 to 1.0 partby weight relative to 100 parts by weight of the sum total of thecomponent (A) and the component (B). If the amount of the component (D)is smaller than 0.01 parts by weight, the composition could not havesatisfactory flame retardancy and its anti-dripping property will bepoor. However, even if the amount of the component (D) is larger than1.0 part by weight, such a large amount of the component (D) added couldnot produce any additional effect but is rather unfavorable in a senseof economy.

[iv] Regarding the relationship between the phosphorus content of thehalogen-free phosphoric ester of the component (C) and the amount of thecomposite rubbery graft copolymer of the component (B), it is necessarythat the ratio by weight of the amount of the composite rubbery graftcopolymer (B) to the phosphorus content of the halogen-free phosphoricester (C), or that is, [amount of the composite rubbery graft copolymer(B)/phosphorus content of the halogen-free phosphoric ester (C)] fallsbetween 2 and 15. Within the defined range, the composition could havewell-balanced physical properties. If the weight ratio is smaller than2, the moldings of the composition could not have satisfactory impactresistance; and if larger than 15, they could not have satisfactoryflame retardancy.

(3) The resin composition of the invention may optionally contain, inaddition to the components (A), (B), (C) and (D) noted above, variousinorganic fillers, additives and other synthetic resins, within therange not interfering with the object of the,invention.

For example, inorganic fillers may be added to the polycarbonate resincomposition for the purpose of improving the mechanical strength and thedurability of the composition. As specific examples of the inorganicfillers, mentioned are glass fibers, carbon fibers, glass beads, glassflakes, carbon flakes, carbon black, calcium sulfate, calcium carbonate,calcium silicate, titanium oxide, alumina, silica, asbestos, talc, clay,mica, quartz powder, etc. The additives include, for example,antioxidants such as hindered phenols, phosphorus compounds (phosphites,phosphates, etc.), amines, etc.; ultraviolet absorbents such asbenzotriazoles, benzophenones, etc.; external lubricants such asaliphatic carboxylates, paraffins, silicone oils, polyethylene waxes,etc.; as well as mold-releasing agents, antistatic agents, colorants,etc. Other resins that may be added to the composition of the intentioninclude, for example, polyethylenes, polypropylenes, polystyrenes, ASresins, ABS resins, polymethyl methacrylates, etc.

(4) Formulation and Kneading of Constituent Components, and Molding ofthe Resulting Composition

Formulation and kneading of the constituent components is notspecifically defined, for which is employable any ordinary method. Forexample, employable are any of ribbon blenders, Henschel mixers, Banburymixers, drum tumblers, single-screw extruders, double-screw extruders,co-kneaders, multi-screw extruders, etc. For kneading the components,the heating temperature may be any ordinary one, for example, fallingbetween 240 and 340° C.

The polycarbonate resin composition thus produced may be molded invarious known molding methods of, for example, injection molding, blowmolding, extrusion molding, compression molding, calender molding,rotary molding or the like. In particular, the composition is suitableto producing moldings in the fields of office automation equipment andelectrical and electronic appliances, concretely, to producing housingsof office automation equipment and electrical and electronic appliancessuch as notebook-type personal computers, etc., and battery packs ofoffice automation equipment and mobile communication appliances such asportable telephones, cellular phone etc.

EXAMPLES

The invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

(1) The materials used in examples and comparative examples arementioned below.

(A) Polycarbonate (PC resin):

Toughlon FN1900A (trade name, from Idemitsu Petrochemical; this isbisphenol A-type polycarbonate having a viscosity-average molecularweight of 19000).

(B) Composite rubbery graft copolymer:

Metablen S-2001 (trade name, from Mitsubishi Rayon; this is methylmethacrylate-alkyl acrylate-dimethylsiloxane copolymer).

(C) Halogen-free phosphoric esters:

[i] Adekastab PFR (trade name, from Asahi Denka Kogyo; this isphenyl-resorcinol polyphosphate having a phosphorus content of 10.8% byweight).

[ii] PX-200 (trade name, from Daihachi Chemical Industry; this is2,6-dimethylphenyl-resorcinol polyphosphate having a phosphorus contentof 9.0% by weight).

(D) Polytetrafluoroethylene:

Algoflon F5 (trade name, from Montefluos).

(E) Bromine-containing flame retardant:

BC-52 (trade name, from Greatlakes), hereinafter referred to as BC-52.

(2) The properties of the oolycarbonate resin compositions produced areevaluated according to the methods mentioned below.

(a) Izod Impact Strength Test

According to JIS K7110, test pieces are tested at −10° C. Of 10 testpieces, the number of those not with brittle fracture but with ductilefracture is counted, from which is obtained the percent ductile fracture(%) of the test pieces. The percent ductile fracture is the index of theimpact resistance of the material tested. Specifically, the impactresistance of the material tested is based on the mode of fracture ofthe test pieces of the material, as to whether the test pieces havingbeen tested in the Izod test have ductile fracture or brittle fracture.The material having a higher percent ductile fracture has higher impactresistance.

(b) Flame Retardancy

The flame retardancy is measured in a vertical combustion test accordingto the UL 94 (Underwriters Laboratories Standards, Subject 94), in whichare tested test pieces having a thickness of 0.8 mm.

(c) Flowability

The flow ability is measure data temperature of 280° C. under a load of160 kg/cm², according to JIS K7210.

(d) In-Mold Thermal Stability

Using a molding machine (IS-25EP from Toshiba Machine), the in-moldthermal stability is measured at a settled temperature of 300° C. for aresidence time of 20 minutes. The samples tested are evaluated asfollows:

S: Silver marks found.

◯: No change.

(e) Gas Generation in Molding

Using a molding machine (IS-25EP from Toshiba Machine), samples arecontinuously molded at a settled molding temperature of 300° C. The gasgeneration, if any, during the molding is checked visually.

Much: Much gas generated.

Little: Little gas generated.

Examples 1 and 2, Comparative Examples 1 to 6

Table 1 shows the components and their amounts used herein. Using a35-mmΦ double-screw extruder at a cylinder temperature of 280° C. and ascrew revolution of 100 rpm, the indicated amounts of the componentswere melt-kneaded and extruded out into pellets. The resulting pelletswere dried at 100° C. for 5hours, and then injection-molded at aninjection temperature of 280° C. into test pieces for measurement ofphysical properties.

The data of the properties of the resin compositions are shown in Table1.

TABLE 1 Examples Comparative Examples 1 2 1 2 3 4 5 6 Components (A)Polycarbonate resin (wt. %) 96 94 94 100 85 99 95 100 (B) Compositerubbery graft copolymer 4 6 6 0 15 1 5 0 (wt. %) The amounts of (C), (D)and (X) are parts by weight relative to 100 parts by weight of (A) +(B). (C) Halogen free phosphoric ester (1) 7 0 0 7 0 10 7 7 (phosphoruscontent) (0.76) (0.76) (1.08) (0.76) (0.76) (C) Halogen free phosphoricester (2) 0 7 0 0 7 0 0 0 (phosphorus content) (0.63) (0.63) (D)Polytetrafluoroethylene 0.5 0.3 0.5 0.3 0.3 0.5 0 0 (X) Brominecontaining flame retardant 0 0 15 0 0 0 0 0 Ratio by weight of amount of5.3 9.5 — 0 23 0.9 6.6 0 (B)/phosphorus content of (C) EvaluationPercent ductility fracture (%) in Izod 100 100 100 0 100 0 100 0 impacttest UL94, 0.8 mm, class V-O passed passed passed passed failed passedfailed failed Flowability (Q value) 22 21 10 25 23 25 23 24 In-moldthermal stability ◯ ◯ S ◯ ◯ ◯ ◯ ◯ Gas generation in molding littlelittle much little little little little little

As is known from Table 1, the samples of Examples 1 and 2 both havehigh-level flame retardancy, and have good impact resistance, goodflowability and good moldability.

As opposed to those, the sample of Comparative Example 1 containing thebromine-containing flame retardant has poor flowability and poormoldability, and generated much gas while being molded. The sample ofComparative Example 2 not containing the composite rubbery graftcopolymer, has low impact resistance. In Comparative Example 3, theratio by weight of the amount of the composite rubbery graft copolymer(B) to the phosphorus content of the halogen-free phosphoric ester (C)is larger than 15, (that is, the proportion of the phosphorus compoundis small). Therefore, the sample of Comparative Example 3 failed in theflame retardancy test. In Comparative Example 4, the weight ratio of (B)to (C) is smaller than 2, (that is, the proportion of the compositerubbery graft copolymer is small). Therefore, the sample of ComparativeExample 4 has poor impact resistance. The sample of Comparative Example5 not containing polytetrafluoroethylene failed in the flame retardancytest. The sample of Comparative Example 6 not containing the compositerubbery graft copolymer has poor impact resistance, and, in addition,not containing polytetrafluoroethylene, this failed in the flameretardancy test.

Industrial Applicability

The flame-retardant polycarbonate resin composition of the invention hasgood moldability and good flowability while having good mechanicalproperties including impact resistance, and, addition, even notcontaining a bromine compound, it has excellent flame retardancy.Therefore, the composition is especially suitable to moldings in thefields of office automation equipment and electrical and electronicappliances, concretely, for housings of office automation equipment andelectrical and electronic appliances, such as notebook-type personalcomputers and others, and also for battery packs.

What is claimed is:
 1. A flame-retardant polycarbonate resin compositioncomprising (A) a polycarbonate resin and (B) a composite rubber graftcopolymer in a ratio by weight, (A):(B), falling between 99:1 and 92:8,and containing, relative to 100 parts by weight of the sum total of thecomponent (A) and the component (B), (C) from 0.3 to 1.2 parts byweight, in terms of phosphorus, of a halogen-free phosphoric ester, and(D) from 0.01 to 1.0 part by weight of a polytetrafluoroethylene, inwhich the ratio by weight of the amount of the composite rubbery graftcopolymer (B) to the phosphorus content of the halogen-free phosphoricester (C) falls between 2 and 15, wherein the composite rubbery graftcopolymer (B) is prepared by grafting a composite rubber, which has astructure composed of from 1 to 99% by weight of a polyorganosiloxanerubber component and from 1 to 99% by weight of a polyalkyl acrylaterubber components, the two components being so intertwisted with eachother as not to separate from each other, and has a mean particlediameter of from 0.01 μm to 0.6 μm, with one or more vinyl monomers,wherein said composition contains essentially no inorganic filler andessentially no ABS resin.
 2. Electrical and electronic components asmade by molding the flame-retardant polycarbonate resin composition ofclaim
 1. 3. Housings of office automation equipment, or housings ofelectrical and electronic appliances, as made by molding theflame-retardant polycarbonate resin composition of claim
 1. 4. Batterypacks as made by molding the flame-retardant polycarbonate resincomposition of claim
 1. 5. A flame-retardant polycarbonate resincomposition consisting essentially of (A) a polycarbonate resin and (B)a composite rubber graft copolymer in a ratio by weight, (A):(B),falling between 99:1 and 92:8, and containing, relative to 100 parts byweight of the sum total of the component (A) and the component (B), (C)from 0.3 to 1.2 parts by weight, in terms of phosphorus, of ahalogen-free phosphoric ester, and (D) from 0.01 to 1.0 part by weightof a polytetrafluoroethylene, in which the ratio by weight of the amountof the composite rubbery graft copolymer (B) to the phosphorus contentof the halogen-free phosphoric ester (C) falls between 2 and 15, whereinthe composite rubbery graft copolymer (B) is prepared by grafting acomposite rubber, which has a structure composed of from 1 to 99% byweight of a polyorganosiloxane rubber component and from 1 to 99% byweight of a polyalkyl acrylate rubber components, the two componentsbeing so intertwisted with each other as not to separate from eachother, and has a mean particle diameter of from 0.01 μm to 0.6 μm, withone or more vinyl monomers, wherein said composition containsessentially no inorganic filler and essentially no ABS resin. 6.Electrical and electronic components as made by molding theflame-retardant polycarbonate resin composition of claim
 5. 7. Housingsof office automation equipment, or housings of electrical and electronicappliances, as made by molding the flame-retardant polycarbonate resincomposition of claim
 5. 8. Battery packs as made by molding theflame-retardant polycarbonate resin composition of claim 5.